Orthotic materials which are used in podiatry must be thin, lightweight, strong and durable. They must also be capable of being easily formed with low heat so as to be custom fitted by the podiatrist. Carbon fabric reinforced acrylic composite orthotics which are now commercially available have good compressive strength at a thickness of about 1.75 mm but are difficult to deform since the composite must be baked in a conventional over until it softens.
Orthotics prepared with thermoplastic resins are often preferred over orthotics prepared with thermosetting resins because composite articles prepared with thermoplastic orthotics can be easily post-formed and reshaped if defects are found whereas articles prepared with thermosetting orthotics cannot be reprocessed or reformed after cure. In the latter instance, the entire article must be scrapped if found defective. In addition, while orthotics prepared with thermoplastic resins have an almost infinite shelf life, prepregs prepared with thermosetting resins have a finite shelf life, usually no more than one year. Furthermore, when hot pressing the latter, extreme caution must be taken in effecting cure to ensure that the reaction proceeds at a proper rate since the amount of heat, heating time and pressure during cure are all extremely critical. No such caution is necessary in the case of thermoplastic orthotics as these materials do not undergo any cure.
Prosthesis devices must also be formable to permit adjustment from the initial fitting and over time when weight loss or gain of the patient affects proper fit.
U.S. Pat. No. 4,868,038 to McCullough et al, which is herein incorporated by reference discloses a composite material of synthetic resin which is reinforced with carbonaceous fibers. However, a composite which can be reformed at a temperature less than 100.degree. C. is not disclosed.
U.S. Pat. No. 4,764,397 to Fischer et al, which is herewith incorporated by reference, discloses various processes which can be used to make the composites of the present invention. However, a composite comprising polyvinyl chloride and halogenated polyvinyl chloride is not disclosed.